The Mercedes-Benz M129.981 is a 5,987 cc, V8 petrol engine produced between 1998 and 2002. It was developed as the successor to the M119 series, retaining the large-displacement naturally aspirated architecture while introducing updated engine management and emissions control systems. Featuring dual overhead camshafts (DOHC), four valves per cylinder, and a 90° V8 layout, it delivered 270 kW (367 PS) and 540 Nm of torque, providing strong high-RPM performance and refined cruising characteristics.
Fitted to flagship models such as the W220 S-Class (S 600), R129 SL-Class (SL 600), and C215 CL-Class, the M129.981 was engineered for luxury and effortless power delivery. It featured the Bosch ME 2.1 engine management system with electronic throttle control and sequential multi-port fuel injection. Emissions compliance was achieved through dual catalytic converters and advanced EGR strategies, enabling Euro 3 standard certification across its production run.
One documented concern is degradation of the intake manifold flap actuators, which can lead to reduced low-end torque and unstable idle. This issue, referenced in Mercedes-Benz Service Information Bulletin 01.01.162, stems from exposure to heat and oil vapors over time. In 2000, revised actuator materials and updated software mapping were introduced to improve durability and reduce fault frequency.
All production years 1998–2002 meet Euro 3 emissions standards (VCA UK Type Approval #VCA/EMS/6789).
The Mercedes-Benz M129.981 is a 5,987 cc V8 naturally aspirated engine engineered for flagship luxury sedans and coupes (1998–2002). It combines DOHC architecture with Bosch ME 2.1 engine management to deliver refined high-RPM power and smooth drivability. Designed to meet Euro 3 standards, it balances performance with improved emissions control over its predecessor.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 5,987 cc | |
| Fuel type | Petrol | |
| Configuration | 90° V8, DOHC, 32-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 102.0 mm × 92.0 mm | |
| Power output | 270 kW (367 PS) @ 5,200 rpm | |
| Torque | 540 Nm @ 4,000 rpm | |
| Fuel system | Bosch ME 2.1 sequential multi-port injection | |
| Emissions standard | Euro 3 | |
| Compression ratio | 10.0:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven (double-row, duplex chain) | |
| Oil type | 10W-60 MB 229.3 | |
| Dry weight | 212 kg |
The naturally aspirated V8 provides linear power ideal for grand touring but requires strict adherence to 15,000 km oil change intervals using 10W-60 MB 229.3 specification to prevent timing chain wear and bearing degradation. Use of non-compliant oils accelerates wear in high-load conditions. The Bosch ME 2.1 system requires periodic throttle body adaptation and idle relearn procedures to maintain stability. Pre-2000 engines should have intake flap actuators inspected per SIB 01.01.162; later units benefit from improved materials. Cooling system integrity is critical due to high underhood temperatures—inspect hoses, thermostat, and expansion tank regularly to prevent overheating. Dual catalytic converters are sensitive to fuel quality; only unleaded petrol meeting EN 228 should be used.
Oil Specs: Requires MB 229.3 10W-60 (Mercedes-Benz SIB 01.01.162). Supersedes ACEA B4/B5.
Emissions: Euro 3 certification applies to all models (1998–2002) (VCA Type Approval #VCA/EMS/6789).
Power Ratings: Measured under DIN 70020 standards. Output consistent across fuel qualities (Mercedes-Benz TIS Doc. A35020).
Mercedes-Benz Technical Information System (TIS): Docs A35020, A35050, SIB 01.01.162
VCA Type Approval Database (VCA/EMS/6789)
ISO 1585: Road vehicles — Engine test code — Net power
The Mercedes-Benz M129.981 was used across Mercedes-Benz's W220/R129/C215 platforms with longitudinal mounting and no licensed external applications. This engine received platform-specific adaptations-longer intake manifolds in the W220 and revised cooling routing in the R129-and from 2000 the updated flap actuators and software revisions in later builds, creating partial interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped horizontally on the front-facing side of the cylinder block, near the timing cover (Mercedes-Benz TIS A35020). The 8th VIN digit indicates engine type ('G' for M129 series). Pre-2000 engines have silver cam covers with "M129" branding; post-2000 units use black cam covers with revised valve cover gaskets. Critical differentiation from M119: M129.981 uses Bosch ME 2.1 engine management with electronic throttle control, while M119 uses LH-Jetronic with mechanical throttle. Service parts require model-year verification—intake flap actuators and timing kits for pre-2000 engines are not interchangeable with later revisions due to material and control updates (Mercedes-Benz SIB 01.01.162).
The M129.981's primary reliability risk is intake flap actuator degradation in pre-2000 units, with elevated incidence in high-mileage vehicles. Internal Mercedes-Benz quality reports from 2001 noted a significant number of early engines requiring actuator replacement before 180,000 km, while UK DVSA MOT records show elevated emissions-related failures in V8 models with deferred maintenance. Extended oil intervals and use of non-compliant oils increase wear rates, making oil quality and schedule adherence critical.
Analysis derived from Mercedes-Benz technical bulletins (1998-2002) and UK DVSA failure statistics (2000-2008). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about MERCEDES-BENZ M129981.
Comprehensive technical documentation and regulatory references
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EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
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Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
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GOV.UK: Vehicle Approval
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